Eschrichtiidae

Eschrichtiidae or the gray whales is a family of baleen whale (Parvorder Mysticeti) with a single extant species, the gray whale (Eschrichtius robustus), as well as three described fossil genera: Archaeschrichtius and Eschrichtioides from the Miocene and Pliocene of Italy respectively,[1] and Gricetoides from the Pliocene of North Carolina.[2] More recent phylogenetic studies have found this family to be invalid, with its members nesting inside the Balaenopteridae.[3][4] The names of the extant genus and the family honours Danish zoologist Daniel Eschricht.[5]

Eschrichtiidae
Temporal range:
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Parvorder: Mysticeti
Family: Eschrichtiidae
Ellerman & Morrison-Scott 1951
Genera
Synonyms

Taxonomy

In his morphological analysis, Bisconti 2008 found that eschrichtiids and Cetotheriidae (Cetotherium, Mixocetus and Metopocetus) form a monophyletic sister group of Balaenopteridae.[6]

A specimen from the Late Pliocene of northern Italy, named "Cetotherium" gastaldii by Strobel 1875[7] and renamed "Balaenoptera" gastaldii by Portis 1885, was identified as a basal eschrichtiid by Bisconti 2008 who recombined it to Eschrichtioides gastaldii.[8][9]

Steeman et al. 2009 found that the gray whale is phylogenetically distinct from rorquals and that previous morphological studies were correct in the conclusion that the evolution of gulp feeding was a single event in the rorqual lineage.[10] In contrast, multiple later studies found the gray whale to fall within the family Balaenopteridae, being more derived than the minke whales but basal to all other members in the family, and reclassified it in Balaenopteridae; the American Society of Mammalogists has followed this classification.[3][4][11]

Evolution

Fossils of Eschrichtiidae have been found in all major oceanic basins in the Northern Hemisphere, and the family is believed date back to the Late Miocene.[8] Today, gray whales are only present in the northern Pacific, but a population was also present in the northern Atlantic before being driven to extinction by European whalers three centuries ago.[12]

Fossil eschrichtiids from before the Holocene are rare compared to other fossil mysticetes. The only Pleistocene fossil from the Pacific referred to E. eschrichtius is a partial skeleton and an associated skull from California, estimated to be about 200 thousand years old. However, a late Pliocene fossil from Hokkaido, Japan, referred to Eschrichtius sp. is estimated to be 2.6 to 3.9 Mya and a similar unnamed fossil has been reported from California.[8]

In their description of Archaeschrichtius ruggieroi from the late Miocene of Italy, Bisconti & Varola 2006 argued that eschrichtiids most likely originated in the Mediterranean Basin about 10 million years ago and remained there, either permanently or intermittently, at least until the Early Pliocene (5–3 Mya),[13] (but see Messinian salinity crisis.)

References

Notes
  1. Bisconti 2008
  2. Pyenson & Lindberg 2011
  3. McGowen, Michael R; Tsagkogeorga, Georgia; Álvarez-Carretero, Sandra; dos Reis, Mario; Struebig, Monika; Deaville, Robert; Jepson, Paul D; Jarman, Simon; Polanowski, Andrea; Morin, Phillip A; Rossiter, Stephen J (2019-10-21). "Phylogenomic Resolution of the Cetacean Tree of Life Using Target Sequence Capture". Systematic Biology. 69 (3): 479–501. doi:10.1093/sysbio/syz068. ISSN 1063-5157. PMC 7164366. PMID 31633766.
  4. "Explore the Database". www.mammaldiversity.org. Retrieved 2021-08-20.
  5. Jones & Swartz 2008, p. 503
  6. Bisconti 2008, Results, pp. 173–174
  7. Strobel 1875, p. 136
  8. Pyenson & Lindberg 2011, Fossil record of gray whales
  9. Deméré, Berta & McGowen 2005, pp. 119–120
  10. Steeman et al. 2009, p. 580
  11. Árnason, Úlfur; Lammers, Fritjof; Kumar, Vikas; Nilsson, Maria A.; Janke, Axel (2018). "Whole-genome sequencing of the blue whale and other rorquals finds signatures for introgressive gene flow". Science Advances. 4 (4): eaap9873. Bibcode:2018SciA....4.9873A. doi:10.1126/sciadv.aap9873. PMC 5884691. PMID 29632892.
  12. Bisconti & Varola 2006, p. 450
  13. Bisconti & Varola 2006, Implications for eschrichtiid fossil record and paleobiogeography, p. 454

Sources
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